MECHANICAL PERFORMANCE OF CELLULAR LIGHTWEIGHT CONCRETE USING FLY ASH AS PARTIAL CEMENT REPLACEMENT

Abstract

Cellular Lightweight Concrete (CLC) is widely recognised for its low density and good thermal insulation performance; however, its relatively low compressive strength limits broader engineering applications. This study investigates the effect of fly ash as a partial cement replacement on the physical and mechanical properties of CLC mortar. CLC specimens were prepared with fly ash replacement levels of 0%, 10%, and 15% by mass of cement using a protein-based foaming agent. The specimens were tested at curing ages of 7, 14, 28, and 56 days to evaluate density, compressive strength, and deformation behaviour. The experimental results show that the incorporation of fly ash significantly influences the strength development of CLC. The 10% fly ash mixture achieved the highest compressive strength of 0.960 MPa at 56 days, exceeding both the control mixture (0.852 MPa) and the 15% fly ash mixture (0.720 MPa). The improvement in strength at the 10% replacement level is attributed to enhanced pozzolanic reactions and improved matrix densification, resulting in a more uniform pore structure. In contrast, a higher replacement level of 15% led to reduced strength development, likely due to dilution of the cementitious content and delayed hydration. Within the investigated range, a 10% fly ash replacement provides an optimal balance between compressive strength and density, indicating its suitability for non-structural to semi-structural lightweight applications. The findings demonstrate the potential of fly ash-based CLC as a more sustainable construction material by reducing cement consumption while maintaining acceptable mechanical performance.